The present invention is related to xe2x80x9cSystem and Method For Detecting Harmonics of RF Broadcast Station Survey Signalsxe2x80x9d, by David G. Worthy, which is incorporated by reference herein.
The present invention relates generally to the identification of radio stations to which radio tuners are tuned. More specifically, the present invention relates to the broadcast of survey signals from a remote location and the detection of the harmonics of the broadcast survey signals to identify the radio stations to which tuners are tuned.
The commercial broadcast industry and businesses which advertise through the radio frequency (RF) broadcast media need to know the sizes of audiences which are tuned to particular stations relative to other stations at particular times. This need has been met primarily through the use of verbal or written audience participation surveys. With respect to radio, a majority of the listening occurs in automobiles. A problem with written surveys is that listeners cannot practically make a record of their listening tendencies while driving.
In order to make a record of listening tendencies while driving, passive electronic RF monitoring equipment has been used to remotely identify the stations to which tuners may be tuned. Generally speaking, audiences"" radio tuners use predetermined signals, such as local oscillator signals, that are related to the frequencies of the respective stations currently being tuned in. The local oscillator signals are broadcast or otherwise emitted from the tuners as very weak signals that sensitive monitoring equipment can detect. The passive monitoring equipment identifies the radio stations to which tuners are tuned by detecting these local oscillator signals.
This remote monitoring technique is desirable because it does not require cooperation from an audience, hence reducing or eliminating a host of inaccuracies and costs associated with audience participation surveys. Furthermore, large sample sizes may be monitored at low cost relative to audience participation survey techniques.
Typically, prior art passive monitoring systems call for the local oscillator signals to be well above the level of background electronic noise in the area at which the remote monitoring is to occur. One primary source of background electronic noise, or interference, is from the radio stations themselves because the radio stations broadcast near in frequency to the desired local oscillator signal, and with much higher power.
The background electronic noise may cause local oscillator signals at some frequencies to be more readily detectable than at other frequencies leading to station bias in favor of stations whose related local oscillator signals may have a lower level of background noise. One attempt to compensate for this station bias is to tune the monitoring equipment to the radio station or frequency with the lowest amount of signal to noise ratio in order to equalize the detection of the noisiest local oscillator signal with the detection of the other less noisy oscillator signals. Unfortunately, such a strategy results in the reduced sensitivity of the monitoring equipment and a reduced number of incidences that a radio station is identified, or counted, through the detection of the corresponding local oscillator signal.
The monitoring equipment may be tuned by using the traffic passing through a detection zone of the monitoring equipment as a signal source for the monitoring equipment. Unfortunately, enough traffic needs to pass through the detection zone, even in low traffic areas, on each frequency for the tuning parameters to be statistically accurate. Accordingly, a tuning process that utilizes passing traffic may undesirably take days, depending upon the level of traffic. Another means of tuning the monitoring equipment is to have personnel take a signal generator to the site of the monitoring equipment. The signal generator can then be used as a signal source that imitates passing traffic in order to tune the monitoring equipment. While this tuning process may be quicker than relying on the passing traffic, it is costly in terms of the wages paid to the personnel and is subject to the scheduling constraints of the personnel. Moreover, as interference conditions change over time, the tuning process should be repeated.
Interference from intermittent transmissions from radio stations, television stations, airports, and so forth may also affect the prior art passive monitoring systems and be erroneously counted by the monitoring equipment. Consequently, significant xe2x80x9cpostxe2x80x9d data integrity checking is employed to eliminate such erroneous counts from the record. Post data integrity checking undesirably drives up the costs of the survey technique and increases the potential for creating error in the survey record.
An active electronic RF monitoring system has also been used to remotely identify the stations to which tuners may be tuned. The active system broadcasts an RF survey signal which is related to an RF carrier signal, or radio broadcast signal. The RF survey signal is configured to cause a radio tuner to emit an audio echo signal from its corresponding speaker. Simultaneously, the audio echo signal is electromagnetically radiated from the radio tuner when the tuner is tuned to the RF carrier signal related to the radio broadcast signal. The active monitoring equipment identifies the radio stations to which tuners are tuned by detecting the electromagnetically radiated audio echo signal. Unfortunately, the audio echo signal may be detected by some survey participants as interference on the radio station.
Accordingly, it is an advantage of the present invention that an active system and method for remotely identifying RF broadcast stations in the presence of significant background interference are provided.
It is another advantage of the present invention that the system and method identify RF broadcast stations by actively broadcasting survey signals and detecting the harmonics of the survey signals.
It is another advantage of the present invention that the system and method remotely obtain audience survey data in a manner that does not interfere with the RF broadcast signals.
It is another advantage of the present invention that an active broadcast capability of the system may be employed to cost and time effectively tune the system.
Another advantage of the present invention is that the active broadcast capability of the system may be employed to facilitate remote communication with the system.
It is yet another advantage of the present invention that post data integrity checking is substantially reduced through the detection of the harmonics of the survey signals.
The above and other advantages of the present invention are carried out in one form by a remote audience survey method for identifying radio stations to which tuners are tuned, the tuners having local oscillator (LO) signals emitted therefrom, and the LO signals being associated with the radio stations. The method calls for selecting one of the LO signals associated with one of the radio stations. The one LO signal exhibits a fundamental frequency. A survey signal is generated in response to the selecting operation, the survey signal being one of the LO signals modified to incorporate a signal identifier. The method further calls for broadcasting the survey signal, receiving a broadcast signal, detecting a harmonic of the fundamental frequency within the broadcast signal, and verifying that the detected harmonic includes the signal identifier to determine that the one of the tuners is tuned to the one radio station.
The above and other advantages of the present invention are carried out in another form by a remote audience survey system for identifying a radio station to which a tuner is tuned, the tuner having local oscillator (LO) signals emitted therefrom. The system includes a controller configured to select one of the LO signals associated with the radio station, the one LO signal exhibiting a fundamental frequency. A transmitter is in communication with the controller. The transmitter includes a signal generator for producing the one LO signal, a modulator in communication with the signal generator for incorporating a modulation characteristic into the one LO signal to form a survey signal, and a first antenna in communication with an output of the modulator for broadcasting the survey signal. A receiver is in communication with the controller and has a second antenna configured to receive a broadcast signal. The receiver is configured to detect a harmonic of the fundamental frequency within the broadcast signal and verify that the detected harmonic includes the modulation characteristic to determine that the tuner is tuned to the radio station.